2.7i compression question

[lovnbmws]

I'm going to be building a naturally aspirated 2.7i using an 87 b25 engine with seta bottom end. From what I’ve read this combination should result in a compression ratio of 8.5:1.

Question: Can the block and/or head be shaved to increase the compression ratio or will doing so result in offsetting the cam timing? If it disturbers the timing can this be corrected?

Before custom pistons are offered as a solution I am trying to do this on an extreme budget while having access to a machine shop. I have time and material to build custom parts here and there but buying high dollar parts are not an option.

[Devil Inc]

If it is truly a SETA bottom end then there won't be a big loss of compression. SETA engines use a variant of the 885 head and the pistons are domed like the b25 ones. Do some searching and you'll find some comparisons of the different combinations.

[devon.818]

search button!

http://lmgtfy.com/?q=seta+bottom+end+with+i+head

[lovnbmws]

search button!
http://lmgtfy.com/?q=seta+bottom+end+with+i+head

Yes I’ve done that, thank you both.

I’ve searched and I’ve read and I found the resultant compression ratio would be 8.5:1 as I stated above. My question is about increasing the compression ratio beyond that without custom pistons.

I have tried searching and found nothing. Perhaps I’m using the wrong key words. Some help would be useful that’s why I posted the question. Please do not assume I am lazy and tell me to use the search button.

[jlevie]

By milling the head the maximum amount you might get the compression ratio up by a tenth or two. But that will require adjusting the cam timing.

The only way to get a significant increase in the compression ratio is custom pistons.

[MR 325]

The Super Eta pistons already sit pretty high on the deck of the block. I wouldn't recommend shaving it down.

[digger]

use eta crank, eta rods and I pistons which sit ~2mm down the block (3mm longer throw and 5mm shorter rod = -2mm). Mill ~2mm off and use a adjustable pulley for any changes in cam timing should get you 9.4:1CR, a bit more if you lightly shave the head.

[Chuckcruzin1986]

I cut .050" off my head

My engine has a 885 head, 2.7 bottom with Super eta pistons. I clayed the pistons and found interferance so I milled more clearance in the pistons. I also installed an adjustable timing gear. I have not driven the car yet but I am very happy with the throttle response and look forward to a little tuning. See my video if you wish :-)
I plan on checking the compression to see how much more pressure there is .......... should be interesting.

http://www.youtube.com/watch?v=Hg-TVYfKZSo

See you on 696

Chuck

P.S. I have had a number of people correct me and say that I cut .005" :yawn: